Damien, Mario,
can you look at this?
----- Forwarded message from Paul Sarraffe <psarraf@xxxxxxxxx> -----
Date: Fri, 31 Aug 2018 16:16:20 +0000 (UTC)
From: Paul Sarraffe <psarraf@xxxxxxxxx>
To: "fedora-kernel-acpi@xxxxxxxxxxxxxxxxx" <fedora-kernel-acpi@xxxxxxxxxxxxxxxxx>
Subject: [acpi] ACPI brightness control on DELL laptop Inspiron N4010 not working after update to kernel 4.17.19
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Kernel update 4.17.19 broke the brightness control on my DELL Inspiron N4010. It worked fine with kernel 4.17.18.
It appears that the following change fixed brightness control on some DELL laptops while breaking it on others:
commit 587eb87b45bb6a97452b9719f63cd489e1371e77
Author: Damien Thébault <damien@xxxxxxxx>
Date: Wed Jul 18 12:06:01 2018 +0200
platform/x86: dell-laptop: Fix backlight detection
[ Upstream commit 2502e5a025935b7b476b69eda4959b3c4022c72b ]
Fix return code check for "max brightness" ACPI call.
The Dell laptop ACPI video brightness control is not present on dell
laptops anymore, but was present in older kernel versions.
The code that checks the return value is incorrect since the SMM
refactoring.
The old code was:
if (buffer->output[0] == 0)
Which was changed to:
ret = dell_send_request(...)
if (ret)
However, dell_send_request() will return 0 if buffer->output[0] == 0,
so we must change the check to:
if (ret == 0)
This issue was found on a Dell M4800 laptop, and the fix tested on it
as well.
Fixes: 549b4930f057 ("dell-smbios: Introduce dispatcher for SMM calls")
Signed-off-by: Damien Thébault <damien@xxxxxxxx>
Tested-by: Damien Thébault <damien@xxxxxxxx>
Reviewed-by: Pali Rohár <pali.rohar@xxxxxxxxx>
Reviewed-by: Mario Limonciello <mario.limonciello@xxxxxxxx>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
----- End forwarded message -----
--
With Best Regards,
Andy Shevchenko
